Many types of additives are used to improve lubricating oil and fuel compositions. Such additives include, but are not limited to dispersants and detergents of the ashless and ash-containing variety, oxidation inhibitors, anti-wear additives, friction modifiers, and the like. Such materials are well known in the art and are described in many publications, for example, Smalheer, et al, “Lubricant Additives”, Lezius-Hiles Co., Cleveland, Ohio, USA (1967); M. W. Ranney, Ed., “Lubricant Additives”, Noyes Data Corp., Park Ridge, N.J., USA (1973); M. J. Satriana, Ed., “Synthetic Oils and Lubricant Additives, Advances since 1979, Noyes Data Corp., Park Ridge N.J., USA (1982), W. C. Gergel, “Lubricant Additive Chemistry”, Publication 694-320-65R1 of the Lubrizol Corp., Wickliffe, Ohio, USA (1994); and W. C. Gergel et al, “Lubrication Theory and Practice” Publication 794-320-59R3 of the Lubrizol Corp., Wickliffe, Ohio, USA (1994); and in numerous United States patents, for example Chamberlin, II, U.S. Pat. No. 4,326,972, Schroeck et al, U.S. Pat. No. 4,904,401, and Ripple et al, U.S. Pat. No. 4,981,602. Many such additives are frequently derived from carboxylic reactants, for example, acids, esters, anhydrides, lactones, and others.
Specific examples of commonly used carboxylic compounds used as intermediates for preparing lubricating oil additives include alkyl-and alkenyl substituted succinic acids and anhydrides, polyolefin substituted carboxylic acids, aromatic acids, such as salicylic acids, and others. Illustrative carboxylic compounds are described in Meinhardt, et al, U.S. Pat. No. 4,234,435; Norman et al, U.S. Pat. No. 3,172,892; LeSuer et al, U.S. Pat. No. 3,454,607 and Rense, U.S. Pat. No. 3,215,707.
Butyl rubbers are polymers of isobutylene and dienes, usually isoprene or butadiene. Butyl rubbers are generally high molecular weight elastomers. At page 392 of Kirk-Othmer Concise Encyclopedia of Chemical Technology, Wiley-Interscience, New York (1985) it is stated that the isoprene in butyl rubber is linked predominantly by 1,4-addition at a level of from about 0.25 to about 2.5 mol per 100 mol of monomers.
Rath et al in U.S. Pat. No. 5,556,932 teach chlorine-free non-drying copolymers of isobutene with C4–C10 dienes having isolated or conjugated double bonds and containing at least 60 mol % of terminal double bonds and a process for preparing same. The polymer is prepared by cationic polymerization wherein the isobutylene is polymerized with the diene with the aid of BF3-alcohol complex.
Rath et al refer to GB-A 2,231,873 A which relates to oil soluble dispersants useful as luboil additives. These comprise a polyolefin substituted dicarboxylic acid or anhydride in which the Mn of the polyolefin is from 1500 to 5000 and the molar equivalent ratio of dicarboxylic groups to equivalents of polyolefin substituent is less than 1.3. The polyolefin substituted dicarboxylic acid or anhydride can be further reacted with amines or alcohols to form other dispersant additives. Rath teaches the copolymer can be reacted according to GB-A 2,231,873 A to give fuel and lubricating oil additives.
Many carboxylic intermediates used in the preparation of lubricating oil additives contain chlorine. While the amount of chlorine present is often only a very small amount of the total weight of the intermediate, the chlorine frequently is carried over into the carboxylic derivative which is desired as an additive. For a variety of reasons, including environmental reasons, the industry has been making efforts to reduce or to eliminate-chlorine from additives designed for use as lubricant or fuel additives.
Accordingly, it is desirable to provide low chlorine or chlorine free intermediates which can be used to prepare low chlorine or chlorine free derivatives for use in lubricants and fuels.
Lubricating oils are used over a broad range of conditions. Particularly difficult are operations under high speed and high temperature and low speed and short duration. The former often results in oxidation of the lubricant while the latter often results in the formation of water-containing sludge. Both of these result in the presence of deposits which can adversely affect engine operation. Dispersants and detergents of the ash containing and ashless type are frequently used to keep such deposits in suspension.
It is also desirable that a lubricating oil composition maintain a relatively stable viscosity over a wide range of temperatures. Viscosity improvers are often used to reduce the extent of the decrease in viscosity as the temperature is raised or to reduce the extent of the increase in viscosity as the temperature is lowered, or both. Thus, a viscosity improver ameliorates the change of viscosity of an oil containing it with changes in temperature. The fluidity characteristics of the oil are improved.
The compositions of the instant invention serve as dispersants for fuels and lubricating oil compositions. It has now been discovered that multigrade lubricating oil compositions, that is compositions which display excellent viscosity characteristics over a wide range of temperatures, can be prepared employing the compositions of this invention.
Typically, multigrade lubricating oil compositions include at least one polymeric viscosity improving agent, frequently a hydrocarbon polymer. Frequently, the amount of polymeric viscosity improver needed to obtain multigrade lubricating oil compositions can be significantly reduced when the compositions of the instant invention are employed as dispersants compared to the amount of polymeric viscosity improver needed to obtain similar viscosity improving benefit when conventional dispersants are used.
Yet another advantage is that with a reduction in the amount of polymeric viscosity improver, the amount of volatile lower viscosity oils in the lubricant is reduced.
A surprising benefit is that the derivatives of this invention provide superior viscometrics when used in lubricants compared to the viscometrics observed when corresponding derivatives derived from high vinylidene polyisobutylenes are employed.
Another surprising advantage of the present invention is the ease of processing during the reaction of the polyene-isobutylene copolymer with α,β-unsaturated carboxylic acylating agents. The ease of processing is better than that observed employing high terminal vinylidene polyisobutylene. Typically, an added polymeric viscosity improver is needed in order to obtain multigrade lubricating oil compositions. These benefits arise without depreciation of dispersancy and low temperature performance.
It has generally been observed that lubricating oil compositions containing highly basic dispersants, i.e., those prepared employing a high level of amine nitrogen per carbonyl of the intermediate frequently suffer from poor elastomer seal, particularly fluorocarbon elastomer performance. Over time, these seals are susceptible to deterioration caused by lubricating oils. Seal deterioration results in oil leaking from the engine. A lubricating oil composition that degrades elastomer seals in an engine is unacceptable to engine manufacturers and has limited value.
Nitrogen containing dispersants of the instant invention have substantially improved seal performance as measured by the Volkswagen PV 3344 Seal Test. Using this test, a fluoroelastomer material is immersed in the oil to be evaluated at 150° C. for a total of 282 hours, the oil being replaced with fresh oil every 94 hours. On termination of the test, the condition of the elastomer sample is evaluated, including the presence of cracking, and the mechanical properties are examined, including tensile strength and rupture elongation.
The carboxylic derivative compositions of this invention provide to lubricants, soot handling characteristics comparable to those provided by much higher Total Base Number (TBN) dispersants, which high TBN dispersants typically do not perform as well on seals. The present invention provides a method for reducing soot induced thickening of lubricating oil compositions comprising incorporating in said lubricating oil composition a carboxylic derivative compositions of this invention.
At higher nitrogen to carbonyl ratios, it has generally been difficult to obtain products that provide significant thickening to a lubricant. Highly basic nitrogen containing compositions of this invention can be prepared that are more viscous and which provide lubricants with additional thickening, employing significantly reduced amounts of additional viscosity improver or even without additional viscosity improver.
With use, a lubricant's viscosity will generally tend to slowly increase. This increase, sometimes referred to as vis-creep, tends to arise due to build up in the lubricant, over time, of soot, insoluble oxidation products and/or other combustion products. In this manner, viscosity is related to lubricant quality. Such an increase in viscosity is indicative of quality degradation.
Lubricants containing carboxylic compositions of this invention tend to resist this undesirable viscosity increase.